Hi Lindsay,
I agree with the opinion that, while there are exceptions, articles are generally more stand-alone ready than posts. In general, blog posts speak continuously to a specific group about a specific topic. They sometimes stray, but the overall trend for most business blogs is fairly consistent. Articles can be vastly different in subject, presentation, length technical level...depending on why and for whom they are written.
I occasionally write for a very small local newspaper. When I write for the food page, my space limitations are extremely tight. I know that if I submit a piece that's longer than 250 words, it is likely to be a victim of the editorial desk chopping block. So I make a point of keeping my writing to about 200 words. However, if I write a feature article for that same paper, I have about twice as much space to work with as well as a much larger spectrum of topics than the food page offers.
Another thing to think about is which audience you want to attract. Let's say most of your current clients are from Target Market A, but you would like to expand your business to reach Target Market B as well. If you craft a series of articles designed to speak to the Bs, you can eventually bring them to your site. But until those Bs are clients, your blog should most likely be written in terms the As would relate to--since they are the folks already coming to your site. Does that make sense?
If you have the time, I see no reason why you shouldn't do both! It'll give you twice the opportunity to demonstrate what you know.